ON THE DECOMPOSING POWER OF HOT STEAM. 189 
<Jliarge withdrawn, and lixiviated repeatedly with hot 
water, (as some of the salt adheres obstinately to the shI- 
phate of lime.) The solution of sulphate of potash is now 
evaporated, observing to remove the sulphate of lime which 
precipitates during the evaporation, from time to time. 
When a cheap, abundant supply of sulphurous acid is at 
command, as in the case of roasting sulphurous ores, the use 
of sulphate of lime or other sulphate may be dispensed with, 
by doubling the quantity of carbonate of lime and exposing 
the charge while at a red heat, to a current of sulphurous 
acid gas and air, (frequently stirring) by which means sul- 
phate of lime is formed during the process, and the sulphate 
of potash is produced as before. 
Muriate of potash (chloride of potassium) is obtained by 
heating potash felspar with muriate of soda, lime, or iron, 
at a temperature above the fusing point of the muriate 
employed. The patentee prefers the muriate of soda, which 
is mixed with an equal weight of finely ground felspar. 
The mixture is well dried and introduced into a horizontal 
iron cylinder, protected by fire brick from the action of the 
fire, having an opening at one end, which is closed by an 
iron door and luted tight. A small hole is made in the 
upper part of the door, which is fitted with a loose plug to 
prevent the bursting of the cylinder fr.om the escape of any 
accidental evolution of gas. The cylinder is kept at a bright 
red heat for six hours, the cover is then removed, and the 
charge raked out as quickly as possible into an iron pot, 
which is immediately covered and kept closed till the mass 
is cool, when it is lixiviated, and the muriate of potash iso- 
lated from the other salt by evaporation and crystallization. 
Chromate of potash is obtained by the following process: 
Four parts by weight of felspar, four parts of lime, or an 
equivalent quantity of carbonate of lime, and one part of 
chrome ore, all in fine powder, are mixed together, placed 
on the hearth of a reverberatory furnace, and kept at a 
bright red heat for eighteen or twenty hours, being properly 
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